This invention concerns a disconnect for electrical circuits. It incorporates a plug and socket combination that provides a convenient and safe way to replace circuit elements in live circuits. A common, but by no means exclusive, application for the disconnect is in non-residential fluorescent light fixtures. Such fixtures require a ballast to operate. Ballasts are typically hard-wired between the power supply and the fluorescent tubes. When a ballast fails it has to be replaced. Traditionally this has been performed by an electrician who cuts the wires to the failed ballast and removes the old ballast. The electrician then installs a new ballast, strips the wire ends, and connects the new ballast's wires to the power supply and tube sockets using suitable twist-on connectors such as those sold by IDEAL Industries, Inc. under their trademarks WIRE-NUT® and TWISTER®. Often this is done in offices, factories, commercial or retail spaces or other facilities where shutting down the power to the fixture is not a practical option. Thus, ballasts are frequently replaced in live circuits. This leaves no room for error on the part of the electrician. Unfortunately, electricians occasionally do make errors which result in personal injury and/or property damage.
The National Electrical Code (NEC) section 410.73(G) addresses the problem of replacing ballasts for non-residential fluorescent fixtures in live circuits. It requires a disconnect that simultaneously removes all conductors of the ballast from the source of supply. It also states that the line side terminals of the disconnect shall be guarded.
The available technology for meeting the NEC requirements includes pin and socket connectors. While such connectors meet the basic requirements they have several disadvantages. They are not rated for solid wire. They require crimping by the electrician. The labor costs of crimping and assembling the connectors is high and the cost of the connectors themselves is high. Insulated terminals provide the lowest cost option but these fail to meet the code requirements of simultaneous disconnect of all wires. Furthermore, insulated terminals are not rated for solid wire and they require crimping by the electrician with its attendant labor cost.
What is needed is a disconnect that fully meets the NEC code requirements but does not add labor cost at the factory or in the field. The technology should be familiar to factory personnel as well as electricians, with no special tools required by either. The disconnect should work with either solid or stranded wire and it should minimize the total installed cost.